Deformation behavior of LPSO phases, grain refinement mechanism, and texture evolution of a Mg-Gd-Y-Zn-Zr alloy processed by forward extrusion combined with dual-directional angular deformation

Abstract

In this study, a Mg-Gd-Y-Zn-Zr alloy was processed by forward extrusion combined with dual-directional angular extrusion (FE-DDAE), and the corresponding microstructure evolution, grain refinement mechanism, and texture were investigated systematically. The deformed materials were subjected to a combination of three-way compressive stress and shear stress, and five different areas were selected to study the typical deformation behaviors. The results show that microstructures are heterogeneous in different areas, and the grain size is refined from 138.70 μm to 37.18 μm through continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX). The block-shaped and lamellar long period stacking ordered (LPSO) phases can coordinate severe deformation through dissolution, tearing, breaking for the former, and bending, severe kinking, refining into small pieces for the latter. Moreover, the broken block-shaped LPSO can promote DRX process through particle-stimulated nucleation (PSN) mechanism, and the lamellar LPSO phases can hinder the dislocation motion to restrict DRX. A strong basal texture is observed during the initial stage of FE-DDAE process, and the basal texture intensity gradually weakens to 4.9 MRD due to the random orientations of high volume fraction of DRX grains. A mixed texture component is formed with basal planes inclined 50° from ED to TD, showing a trend of spreading.